Field of the Invention
The present invention relates to a polarization information acquisition unit that acquires polarization information.
Description of the Related Art
Polarization information of polarized light, whose oscillating direction changes by a reflection on an object and a transmission through an object, is useful for the evaluation and examination of the object. Japanese Patent No. 4974543 discloses a polarization imaging apparatus that includes a stack of a periodic structure on pixels and a dielectric multi-layered film thereon which serve as a polarizer that transmits polarized light corresponding to the orientation of the periodic structure. This polarization imaging apparatus can two-dimensionally acquire polarization information of an incident light flux. Japanese Patent Laid-open No. 2005-221620 discloses a polarization conversion device that changes the state of incident polarization light into an arbitrary state by arranging half-wave plates and quarter-wave plates in series and by rotating each component to reproduce a desired polarization state. “Simultaneous Acquisition of Phase-stepped Fringes Using a Pixelated Micro-retarder Array”, Satoru Yoneyama et al., Journal of the Japanese Society for Experimental Mechanics, Japanese Society for Experimental Mechanics, September 2006, Vol. 6, pp. 275 to 281, discloses a method of performing a phase analysis on an interference pattern and a photoelastic fringe based on an image obtained by single image capturing by arranging a phase plate array and a uniform polarizer on pixels.
However, the polarizer disclosed in Japanese Patent No. 4974543 transmits only linear polarization light and thus cannot detect circular polarization light, for example. The polarization conversion device disclosed in Japanese Patent Laid-open No. 2005-221620 can acquire circular polarization light, but this acquisition is time-divisional and requires a rotation. Therefore, it takes a long time to acquire the polarization information. The method disclosed in Yoneyama et al. has low detection accuracies of linear polarization light and phase information.